Master cylinder relief valve



Jan. 1, 1952 A. B. SEPPMANN MASTER CYLINDER RELIEF VALVE Filed Nov. 20, 1948 %/f MV/M was Patented Jan. 1, 1952 UNITED STATES PATENT OFFICE MASTER CYLINDER RELIEF VALVE Alfred B. Seppmann, Mankato, Minn.

Application November 20, 1948, Serial No. 61,199

4 Claims.

1 This invention relates to a relief valve designed primarily for inclusion in a master brake cylinder, although the valve may be incorporated in other devices. 7

In general, such a master cylinder includes a cylinder proper, a piston in the cylinder for forcervoir, and by a special construction and arrange-.

ment of the piston, a portion of the oil is forced under high pressure into the brake shoes. The passage between the cylinder proper and the reservoiris controlled by a relief valve.

The present invention has to do with a novel relief valve for controlling the flow of oil between the cylinder proper and the reservoir.

An object of the present invention is the provision of such a relief valve having a novel needling valve control of the oil flowing therethrough.

Another object is the provision of a novel relief valve having an oil passage and a valve closure therefor. and a needling control element separate from said valve closure and disposed in said passage. a 7,

In master cylinders, oil mustflow from the reservoir into the piston cylinder on the return of the piston from the power. stroke.

It is therefore another object of the invention to provide a relief valve having a novel construction for controlling the flow of oil from the reservoir to the piston cylinder.

The relief valve of the present invention includes a valve chamber having passages or ports communicating with the piston cylinder and with the reservoir, and a valve closure in the chamber controlling the flow of oil through the passages.

Still another object is the provision of an additional passage or port communicating between the valve chamber and the piston cylinder for providing for rapid flow of oil from the valvechamber into the piston cylinder on the return of the piston from the power stroke.

With these and other objects inyiew, my invention consists in the construction; arrangement and combination of the various parts of my device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawings, wherein;

Figure 1 is a longitudinal sectional view of a master cylinder embodying the present invention;

Figure 2 is an elevational view of the relief valve of the present invention; V

Figure 3 is an exploded View illustrating the relief valve and certain parts thereof Figure 4 is a, view taken on line 4-4 of Figure 3; and s v Figure 5 is the bottom view of Figure 2.

Referring now in detail to the drawings,. the

master cylinder in which the relief ,valve of the present invention is incorporated is shown as a whole in Figure 1; such a master cylinder is employed in such instances as in automobiles and;

is connected with the braking system where on actuation of the master cylinder oil is forced T into the brake lines and the brake shoes are outwardly of the shoulder I6 is an interiorlythreaded portion l8 which is slightly larger than the main cylinder proper. Adjacent the other end of the main cylinder is another shoulder 20 of greater radial extent than the shoulder I6,

which forms a reduced cylindrical portion 22 in the main cylinder. 1

A main movable piston 24 is fitted in the main cylinder, being slidable thereintothrough the open end of the cylinder from the right. The

main piston 24 includes a hollow cylinder 26 having ports 28 adjacent its inner end. Surrounding the cylinder 26 intermediate the ends thereof is an annular flange 30 which is nearly of the same diameter of the main cylinder [4 but freely slidable therein. Next to the flange 30 is a groove cup leather 36 having an inturned flange 38 sur- A further object is the provision of novel valve means for stopping the flow of oil through said additional passage in the reverse direction from that intended, i. e., from the piston cylinder into the valve chamber.

extend into the reduced diameter and is provided at its outer end with-faiieavity 40.

rounds the movable piston with 'thegflange 38 secured in the groove 32.

The cup --leather 35 provides sealing engagement with -the'cylinder L4. The left end of the piston Zlisadapted to linder '22 At one end is a A plunger 42 extends into the cavity 40, the plunger being actuated by the brake pedal of the car. The left end of the movable piston 24 is provided with a peripheral groove 44 having a deeper groove 46, in which is seated the flange 48 of a cup leather 50. The leather 50 bears against the wall of the reduced cylinder 22. Around the left end of the housing I2 is a flange 52 by which the master cylinder as a whole may be mounted in position.

A stationary piston 5.4 is secured in the opposite end of the main cylinder I4. The piston 54 includes a main portion 56 having a central lon.- gitudinal bore 58. One end of thepiston 5,4. is provided with a radial flange 60 on opposite sides of which are sealing gaskets 621 A com-- pression spring 63 is biased between the movable piston 24 and the flange 60 of" the stationary piston 54, surrounding a portion of. each; of the pistons. A fitting 64 having exterior threads is threaded into the threaded portion. I8. and against the outer, gasket 62 and, retains the pis..-. ton; 54 in position in the maincylinder. I4.. Theinner end. of the fixed" piston 54 extends, into the interior ofthe; cylinder 26' which iorms aL nor-- tion of, the, main piston 24. and is there provided with a flange 66 which is of substantially the. same diameter as the inner diameter of the. cylinder 26.. The flange 66' is provided with a.plu.

rality' of axially extending ports 68. To the left.

of the flange 66 is a groove 10 in which. is. received the flange 12 of a cup leather 1,4. The leather 14 hassealing engagement with the. inner' surface of thecylinder 26. anda compression, spring. 16 is biased between the gasket 14 and the inner end of the hollow of the cylinderv 26. The fitting 64.,is providedwith a threadedbore I6 in which is threaded. an insert 80. havin a central bore 82 communicflfingwith a cavity 84. inthe fitting 64. A disk 86,. suchasrubber i. otherflexible material is seated. against. the.v floor of the cavity 84 andhasa centrallhanefifl. in substantial registration with. the bore. 8.2,. A. retarding valve indicated generally at. 8,5 in.- cludes the disc 86 and a cup shap d member 90... The cup shaped member 911- has. a. peripheral. flange 32, around its open side adapted to. fit.- against thedisc 86". A cup. shape. fi e xib le.mem ber 94, such as rubber is fittedin the cup shape. member-60. and secured'thereto as by a, rivet 9 6.' The peripheral wall of themember 90, has a plurality f ports 9.8, A, compression spring I 00,. isjcompressed between the fiangefl92' and; the

piston 54, the latter having a cavity l,02 for receiving the spring. Thespring I00; biases the'retardingvalve to the right. p A The master cylinder is also provided with reservoir I04 which is fgrmed as an integral portion of the main housing-of the master; cylinder. A portion ofthe housing I2; forming the dividingwall between the. cylinder I4 is indicated at I06. The dividing wall I06 'is provided with an enlarged port I08 adjacent the; shoulder 20' and a smaller bore IIO spaced ashort distance therefrom. The wall I06 is also provided with a larger opening I I2 having interior threads there? a inin which is inserted a reliefj valve H4. The. relief valve I I4 comprises the present invention and will b'edescribed in detail presently. An opening I I6' is formed in the reservoir housing in substantial register with ports I08 and I I0 and is'closed by-a snap disc I I8. The Wall iorn ing' the reservoir is als'd'provid ed with another opening I20 having interior threadsand is closed threaded into the opening I20. Above the threaded portion is a flange I26 having engagement with a gasket I28 which in turn engages the housing and seals the cap I22 at this point. The cap I22 is provided with a cavity I30 having a small bore I32 leading to atmosphere. The lower end of the cavity is substantially closed by a disc I34 fitted in a recess in the cap. The disc I34 has an opening I36. It will be noted that theopening I20.- is in register with the relief valve I I4. I

The relief valve I I4 is essentially a chambered body and includes an enlarged upper portion I38 of, cylindrical. form and a lower reduced portion I40' having exterior threads and threaded in the opening H2. The upper portion I38 has an interior cavity I43 formed by cylindrical wall I42. Adjacent the bottom "of the wall I42 are a plurality of ports I44 and above these ports are additional ports I46 both of which communicate between thev interior of the chambered body. and

central upstanding, boss I48..

valve closure member I50. and its other end is engaged by a cap. I56 threaded inthe upper interiorly threaded end of the wall I42 which. is

otherwise open.

The lower end of the chambered body I38 is provided with a centralrelief passage I56 which is bored through the boss I46 and through the 3,5. chambered body and through a projection I60 I64 having an upper cylindrical portion I66 and' a lower tapered portion I68. The upper cylindrical. portion I66 is, of lesser diameter than. the relief passage I5.8., The downwardly extending projection I60 is provided with a, transverse hole I10 for the reception of a cotter key I12. The

hole I10 and the cotter key I12 are of lesser. diameterthan the relief passage I58 to permit the flow of oil through the passage.

ping'out of the relief'passage.

In the lower part of the chambered body. I361 are a plurality of return passages I" which; communicate with the reservoir I04, bypassingthe interior I43"of-' the chambered body and open out the flat under face I62 of the relief valve,

' where they are adapted to communicate with the interior of the main cylinder proper-'14.

tween the interior of the chamberedbody I 38',

and the cylinder I4, opening-out throughthen'at' member which is in the form of'a disc of flexible material such as rubber or a rubbercompound. The disc I18 is'provided with a central opening I adapted to'fit'overthe projection I60 whereby the disc seats against the fiat under face of" the chambered body. A spiral spring; I82;hav-

ing anormalsha'pe as shown in Figure 3 isscated' keyl'lliv M.

Operation- Pietra. 1 j illustrates the. p t master.-

by" a'cap I'I2' having a threaded portion I24 75, cylinder when in retracted position. When the.

The cotterkey I12 prevents the needling pin I64 from drop:

cylinder. Since the cylinder I4 is of greater diameter than the cylinder 26, there is greater displacement in the cylinder I4, and the excess oilin the latter is forced through the ports 68 and past the cup leather 14 which flexes under the pressure of the oil. Thus a considerable volume of oil passes through the bore 58 into the braking system, i. e., a volume greater than the displacement within the cylinder 26. The spring I54 in the relief valve H4 is given a predetermined compression by setting the cap I56. The valve closure member I50 is seated against the boss I48 and closes the relief pas-1 sage I58. In the initial movement of the piston 24, the pressure of the spring I54 is great enough to prevent any oil from passing through the relief passage I58. Also in the initial movement of the piston, the reaction of the brake shoes is not great, this portion of the movement being Ill 111,

lized to take up the slack in the brake shoes.

When the brake shoes engage the brake drums, considerably greater reaction pressure is formed,

and this reaction pressure is exerted through the oil and through the relief passage I58, and when the pressure is great enough it raises the valve closure member I50 against the action of the spring I54. When the latter action takes place the oil in the cylinder I4 instead of passing through the ports 68 passes through the relief. passage I58 and the pressure exerted on the brake shoes is only that caused by the displacement in the cylinder 26. The retarding valve 85 permits the passage of oil in both directions. When the brakes are being applied the oil from the port 58 passes through the holes 98 and flexes the flex ible member 94 and then passes through the bore,

82 into the brake lines. If the operator wishes to create sudden and successive impulses he permits the main piston to be retracted and immediately reapplies the brake. During these momentary movements of the piston, the spring I00 prevents the retarding valve from immediately opening, and thereby enables additional quanti ties of oil to pass from the cylinder I4 into the cylinder 26. However when the brake is released, the force of the oil returning from the brake line, after an interval of time, compresses the spring I00 and permits the oil to return into the master cylinder. The excess oil in the lines passes through the ports 28. 1.

When oil passes through the relief passage I58 when the brakes are applied, as explained above, it tends to raise the needling pin I64. The oil also engages the under face of the valve clo' sure member I50 and raises the latter, whereby the oil passes into the cavity I43 and when sufficient oil enters the cavity the valve closure member is raised above the ports I44 and the oil then passes into the reservoir. closure member I50 is raised sufficiently high, the needling pin I64 extends partially above the. boss I48, and the tapered portion I68 produces a restricting action to the passage of oil. Thus the flow of oil through the relief passage I58 can be more accurately controlled due to the variable action of the tapered portion of the pin. In the retracting action of the movable piston 24 the pressure is reduced in the cylinder I4 and oil then passes from the reservoir through the re- After the valve 6:. turn passages I14 into the cylinder |4.- The flexible disc I18 is flexed downwardly under such flow of oil and permits the oil to pass into the cylinder, but oil is prevented from flowing in the opposite direction by the flexible .valve' disc I18.

The supplemental passage I16 forms an essential of the present invention. In the retracting movement of thepiston 24, pressure is relieved under the main closure element I50 and while most of the oil otherwise would flow through the,

relief passage I58 there would be a certain portion remaining below the upper end of the boss I48. This oil is thus permitted to return through the supplemental passage I16 and permit the valve closure member to seat quickly on the ,boss I48, and quickly close the upper end of the relief passage I 58.

The flat under face I 62 of the relief valve also forms an essential of the present invention. The valve disc I18 is adapted to readily seat against the face I62 and thereby prevent the flow of oil through the passages I14 and I16 in the wrong directions. The spiral spring I82. is adapted-to effectively retain the valve disc I18 against the fiat face I62.

The relief valve is of general utility and may be incorporated in devices other than master cylinders for brakes; accordingly the claims may be construed accordingly, and for purposes of interpreting the claims, the flat under face I62 which is exposed to the interior of the cylinder I4, is considered the first surface, and the outer cylindrical surface of the wall I42 of the chambered body which is exposed to the interior of the reservoir I04, is'considered the second sur-' face. I

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purl. A relief valve for mounting in an opening: between a pair of chambers, comprising, in com bination, a chambered body having a first surface exposed to the interior of one of the chambers and a second surface exposed to the interior of the other chamber, said chambered body having a passage leading from the interior thereof and opening through said first surface, said chambered body having ports leading from the interior thereof and opening through said second surface, a closure member in said chambered body adapted to close said passage. and ports, said chambered body having return passages opening through both of said surfaces and bypassing the interior of said chambered body, said chambered body having a supplemental passage leading from the interior thereof and opening through said first surfaces, a flexible disc secured to said chambered body over said return passages and supplemental passage and subject to pressure exerted against adjacent said first surface, and spring means secured to said chambered body and biasing said flexible disc into position closing said return passages and supplemental passage.

2. A relief valve for mounting in an opening between a pair of chambers, comprising, in combination, a chambered body having a first surface exposed to the interior of one of the chambers and a second surface exposed to the interior E at the other chaanbensaidi chambered: body; hav.-

ing: a passage; leading; from, the; interior: thereof and. opening through, said. first surface; said; chambered body. having ports: leading: from the: interior thereof and opening through; said, second; surface, a closure member in said chambered;

bodyadapted: to close; said: passage. and; ports,

said chambered bodyhaving, return passages;

opening through both of; said; surfaces and; bypassing the interior of saith chambered body; said chambered body: having a; supplemental passage leading from the interior: thereof and opening;

through said first surface, said first surface being aflat face, saidreturn passagesand supplemental passage opening through said, fl'at face, said flat face having a. central projection thereon, a flexibl'edlsc having a; central opening secured to said projection and engageable with saidfiat face, and a. spiral spring secured to said projection and engageable with said flexible-disc.

3. A relief: valve for mounting in: an opening betweerr a pair of chambers, comprising; in combination, a chambered body having afirst surface exposed tothe interior of one of the chambers and asecond' surface exposed to the: interior of the other chamber, said chambered body having-a passage leading from the interior thereof and opening through said first surface, said chambered body having ports leading from the interior thereof: and opening-throughsaid second surface, a closure-member insaid chambered body adapted to close said passage and ports, said chambered body having-return passages opening through both of said: surfaces and bypassing theinterior of said chambered body, saidfirst surfaceexposed to. the interior, of one of the chambersand a second, surface, exposed. to the. interior of,

81 the other: chambers; said first-surfacebeingra: fiat: face, a central: projection o'nJsaidi flat face-,1 said: chambered body having a. relief passage, leading from the, interior thereof; and, opening through saidv first:surface, saidrelief passage terminating in a boss on the innersurface of said chambered. body; said chambered body: having,

portsleadingfrom the interiorthereof and open-,-

ing through said second surface, a valve closure in said chambered body adapted to close said; ports and having a resilient surface engageable with said boss. for closing said relief passage, a. tapered pin slidably positioned insaid relief passage, said chambered body having a plurality of ;return passages opening through both of said surfaces and bypassing the interior of'said' chambered body, said chambered body havinga supplemental passage leading fromthe interior" thereof and opening through said first surface; said return passages and said supplemental pas,- sage opening through said flat face; a flexibledisc having a central opening secured to said projection and engageable' with said flat face, a spiral spring secured to said projection and engageable with said flexible disc, and a keyin a transverse hole in said projection for securingsaid spiral spring in position and retaining said tapered pin in said relief passage, saidpin being" of a thickness less than the transverse dimension of said relief passage.

ALFRED B. SEPPIVLANN.

REFERENCES CITED The following references arev of record in the. file of this patent;

UNITED STATES. PATENTS Number Name Date 2,166,742 Lambert July-18, 1939, 2,170,851 Carroll Aug. 29, 1939' 2,173,979 Picut- Sept. 20,1939 2,216,847 Loweke Oct. 8, 1940; 2,374,235 Roy Apr. 24, 1945 FOREIGN PATENTS Number Country Date 528,131 Germany of 1928 

